Tanner’s gambit was based as much on desperation as it was on his marginal understanding of what was happening inside the bomb.
Of the two kinds of devices Takagi could have built, the gun-type bomb would have been the easiest to disarm. Prevent the uranium bullet from being shot into the pit, the weapon fails to reach critical mass, and there is no detonation.
The kind of weapon Tanner faced, however, was an implosion type.
Inside the steel sphere lay a pit of stable uranium, surrounded by a second sphere known as the soccer ball, which consists of seventy-two octagonal lenses of plastic explosive, each a flawlessly designed shaped charge. Upon detonation, these lenses explode inward with equal force, leaving the pit nowhere to go but deeper inside itself, an event similar to the process that takes place inside the sun’s own internal furnace: Gravity (in a bomb’s case, exterior force) compresses hydrogen atoms until they split into helium, which in turn generates thermonuclear fusion.
Powerful as an implosion bomb is, however, it has an Achilles’ heel: If even one of the explosive lenses fails to detonate or detonates a split second later than its counterparts or directs its force a millimeter off center, the pit escapes the implosion and fails to reach critical mass.
When Tanner pulled the clock’s trigger, two things happened simultaneously.
The impact of the slug against the sphere’s shell sent a shock wave through the gun and up his arm, shattering bones and rapturing blood vessels as it went. Tanner was thrown backward.
Next, the flattened slug did not penetrate the sphere but rather created what is called the sprawl effect as the tightly focused jolt broke loose a scab from the sphere’s inner wall. Traveling at 2,500 feet per second, the BB-sized particle embedded itself in one of the lenses and tore it from the face of the soccer ball.
Two seconds later, the bomb detonated.
In a flash of orange, the sphere exploded. No longer focused inward, the force found the weak spot in the sphere’s wall and blasted through. With a whoosh, a ten-foot jet of white flame shot from the quarter-sized hole, passed over Tanner’s head, and seared the aft bulkhead.
He felt the heat and concussion wash over him. He rolled into a ball, threw himself flat, and covered his face. The jet flared briefly, turned blue, then withdrew back into the sphere with a final whoosh.
Silence.
Tanner groaned and rolled onto his back. Blackness swirled in his eyes. He was tired, so tired. … He turned his head. Through the cargo hatch, he could see the ocean’s surface and beyond that, a slice of blue sky. In the distance, ships and helicopters crisscrossed the water.
Water began pouring over the hatch combing. He watched absently as it rolled across the bulkhead, pushing debris and bodies before it. He reached out and touched the leading edge. The water felt cool. Soothing. God, he was tired. He would lie here for a while, he decided. Just for a little while. …
“BRIGGS! Briggs, damn it!”
Tanner opened his eyes. The square of sky was smaller now and partially blocked by a blurred yellow shape. What was it? He squinted, then blinked until the shape resolved into a raft. The person in it was waving at him.
“Briggs! For God’s sake, move your ass!”
Bear. …
Without thinking, moving on instinct alone, Tanner rolled onto his stomach, pointed himself toward the hatch, and began paddling with his one good arm. A wave broke over his head. Seawater poured into his throat and nose. He coughed, gulped again, sputtered. He paddled harder. He felt himself slipping, being drawn down. He reached for the surface, but it seemed so far away. Too far. Just let it go. The blackness began closing in.
And then a pair of hands appeared in the water and reached for him.